1. Field of the Invention
The present invention relates to a spindle structure of a motor rotor, and especially to a motor rotor having double insulation function and capable of suffering from a large twisting force so as to be manufactured conveniently,
2. Description of the Prior Art
With reference to FIG. 4.about.6, a prior art spindle of a motor rotor is illustrated. A plurality of silicon steel pieces 44 are installed around the spindle 40. Two ends of the spindle 40 are installed with sun plates 46 for clamping the silicon steel pieces 44. An insulating layer 42 made of BMC (a thermosetting plastics) is formed at the periphery of the metal spindle 40, then the spindle 40 of the insulating layer 42 passes through the silicon steel pieces 44 by tightly matching the two components. After all the components of the rotor are assembled, copper wires winds around the silicon steel pieces 44. A bearing, a rectifier, a fan, etc, are installed at the spindle 40 for forming a complete motor.
Moreover, the spindle 40 of a motor rotor is formed by metal. The spindle 40 and the silicon steel pieces 44 are manufactured individually. Then, the spindle 40 is tightly matched with the silicon steel pieces 44. Therefore, when the centers of the spindle 40 and the silicon steel pieces 44 are not well aligned, after assembling the spindle 40 and the silicon steel pieces 44, it is necessary to modify the silicon steel pieces 44 in order that centers of the spindle 40 and the silicon steel pieces 44 can be aligned. If the spindle 40 and the silicon steel pieces 44 are not aligned, the silicon steel pieces 44 will be modified with a large degree so that the outer diameter of the silicon steel pieces 44 is reduced. Thus, the gaps in the rotor become large so that the magnetic flux is affected and so thus the efficiency of the operation of the motor.
In such a prior art motor rotor, although an insulating layer 42 may be formed between the metal spindle 40 and the silicon steel pieces 44 so that the draining current will not flow to the spindle 40 through the silicon steel pieces 44. Therefore, two insulation functions are formed. However, since the combining strength of the insulating layer 42 made of BMC and other material and the spindles 40 is smaller than that of the metal spindle 40 and the silicon steel pieces 44. As a consequence, during operation of the rotor in the larger twisting force, the spindle 40 will easily rotate with respect to the silicon steel pieces 44 so that angle shifts are generated between the rectifier and the silicon steel pieces 44. Thus, the electromechanical angle of the motor operation is affected. Therefore, such a motor rotor spindle 40 having the function of dual insulation can not be used in a motor operating in a large power. The applications are confined largely.
Alternatively, when an insulating layer 42 is formed on the metal spindle 40, as that described above, the combination strength between the insulating layer 42 and the silicon steel pieces 44 is smaller, in order to avoid that a relative rotation is generated between the motor 40 and the insulating layer 42. A pressed texture 402 is formed on the surface of the metal spindle 40 (as shown in FIGS. 5) for increasing the friction force between the metal spindle 40 and the insulating layer 42 so that the metal spindle 40 will not rotate with respect to the insulating layer 42. However, the pressed texture 402 on the surface of the metal spindle 40 will cause some discharging tips are formed on the surface of the spindle 40. Therefore, once the rotor electrically operates, a tip discharging will possibly generate, and thus the insulation of the motor becomes worse.
Moreover, despite of a motor with a metal spindle 40 having an insulating layer 42, the sun plates 46 at two sides of the silicon steel pieces 40 are engaged with the spindle 40, respectively, after the spindle 40 is combined with the silicon steel pieces 42, respectively. Thus, not only the manufacturing process of the motor rotor is increased, but also since the sun plate 46 have a thickness and a length without being adjusted, once an error is occurred in the length of the silicon steel pieces 44, then an error is formed between the length of the silicon steel pieces 44 plus the sun plate 46, respectively, and the winding length of the rotor, and therefore, the magnetic flux of the rotor is affected.
Furthermore, since the spindle 40 or the insulating layer 42 and the silicon steel pieces 44 are engaged tightly, thus the size control between the spindle 40, the insulating layer 42 and the silicon steel pieces 44 must be careful. Once a large error is generated, then a large gap is formed between the spindle 40, or the insulating layer 42 and the silicon steel pieces 44, respectively. Thus, a relative rotation is possible generated between the spindle 40 and the silicon steel pieces 44, respectively, so that a bad operation efficiency of the motor is induced. Therefore, when the rotor is manufactured, a precise size control must be performed and thus the manufactured process is complicated and troublesome.